In convention technology, coal is used to produce coral gas, natural gas, or used to produce gas by coking at high temperature, medium temperature or low temperature. However, the above-mentioned process is required to block pulverized coal or sift lamp coal, as a result, it increases the cost of raw material, or cause the produced gas without a high heat value, a big additional value, and a significant economy and social benefits. The heating methods of furnace can be classified as external-heating style, internal heating style and hybrid-heating style. Specifically, the heating medium in external-heating furnace is not contact directly with raw materials and heat is conducted from furnace wall. The heating medium in the internal-heating furnace contacts with the raw materials directly, and the heating methods are classified as solid heat carrier style and gas heat carrier style according to different heat mediums. In order to attain more purified coal decomposed gas, the heating source part extends out of a channel for impelling and decomposing coal in a shape of flame gas pipe so as to get more purified coal decomposed gas. However, in practical production process, on the one hand, the manufacturing process for each close-packed heating pipe is very complicated and there would be some problem of leakage and cross-channeling in this kind of sealing model, which may cause a potential safety problem. In particularly, the problem of double rotation high temperature airtight between flame gas converged pipe of the flame gas heating pipe and coal decomposed gas collecting pipe also blocks a fast development of decomposition equipment. In addition, the combustion chamber which has problems easily is set inside of the kiln body, so it is not convenient for inspection, overhaul and timely mastering combustion dynamic thereof, and thus increasing the quantity of security blind spots.